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.\"	@(#)minherit.2	8.1 (Berkeley) 6/9/93
.\"
.Dd June 9, 1993
.Dt MINHERIT 2
.Os
.Sh NAME
.Nm minherit
.Nd control the inheritance of pages
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/mman.h
.Ft int
.Fn minherit "void *addr" "size_t len" "int inherit"
.Sh DESCRIPTION
The
.Fn minherit
system call
changes the specified range of virtual addresses to have the specified
fork-time inheritance characteristic
.Fa inherit ,
which can be set to
.Dv MAP_INHERIT_NONE ,
.Dv MAP_INHERIT_COPY ,
or
.Dv MAP_INHERIT_SHARE .
Also possible is
.Dv MAP_INHERIT_DEFAULT ,
which defaults to
.Dv MAP_INHERIT_COPY .
Not all implementations will guarantee that the inheritance characteristic
can be set on a page basis;
the granularity of changes may be as large as an entire region.
.Pp
Normally, the entire address space is marked
.Dv MAP_INHERIT_COPY ;
when the process calls
.Fn fork ,
the child receives a (virtual) copy of the entire address space.
Pages or regions marked
.Dv MAP_INHERIT_SHARE
are shared between the address spaces, while pages or regions marked
.Dv MAP_INHERIT_NONE
will be unmapped in the child.
.Sh SEE ALSO
.Xr fork 2 ,
.Xr madvise 2 ,
.Xr mincore 2 ,
.Xr mprotect 2 ,
.Xr msync 2 ,
.Xr munmap 2
.Sh HISTORY
The
.Fn minherit
function first appeared in
.Ox .
.Sh BUGS
If the a particular port does not support page-granularity
inheritance, there's no way to figure out how large a region is
actually affected by
.Fn minherit .